diff --git a/client/src/components/app.riot b/client/src/components/app.riot
index 9fd1dee..6700488 100644
--- a/client/src/components/app.riot
+++ b/client/src/components/app.riot
@@ -224,6 +224,7 @@
                       mentions: [],
                       is_ai: true,
                       streaming: true,
+                      avatar_hash: '',
                     },
                   })
                   this.scrollToBottom()
diff --git a/client/src/components/chat-room.riot b/client/src/components/chat-room.riot
index 396751f..d59ceed 100644
--- a/client/src/components/chat-room.riot
+++ b/client/src/components/chat-room.riot
@@ -54,7 +54,15 @@
           <span class="member-role ai-role">AI</span>
         </div>
         <div each={member in props.room?.members} key={member.id} class="member-item">
-          <div class="member-avatar">{member.display_name?.charAt(0).toUpperCase()}</div>
+          <div class="member-avatar">
+            <img src={avatarFromEmail(member.email, 28)}
+                 alt={member.display_name}
+                 width="28"
+                 height="28"
+                 class="avatar-img"
+                 loading="lazy"
+            />
+          </div>
           <span class="member-name">{member.display_name}</span>
           <span if={member.id === props.room?.created_by} class="member-role">Owner</span>
         </div>
@@ -222,6 +230,14 @@
       font-size: var(--text-xs);
       color: var(--text-secondary);
       flex-shrink: 0;
+      overflow: hidden;
+    }
+
+    .avatar-img {
+      width: 100%;
+      height: 100%;
+      border-radius: var(--radius-full);
+      object-fit: cover;
     }
 
     .member-item .ai-avatar {
@@ -413,8 +429,11 @@
 
   <script>
     import { ws } from '../services/websocket.js'
+    import { avatarFromEmail as _avatarFromEmail } from '../services/avatar.js'
 
     export default {
+      avatarFromEmail: _avatarFromEmail,
+
       state: {
         inputValue: '',
         typingDisplay: '',
diff --git a/client/src/components/chat-sidebar.riot b/client/src/components/chat-sidebar.riot
index f4ed8d1..952bfde 100644
--- a/client/src/components/chat-sidebar.riot
+++ b/client/src/components/chat-sidebar.riot
@@ -34,7 +34,13 @@
     <div class="sidebar-footer">
       <div class="user-info">
         <div class="user-avatar">
-          {props.user?.display_name?.charAt(0).toUpperCase()}
+          <img src={avatarFromEmail(props.user?.email)}
+               alt={props.user?.display_name}
+               width="32"
+               height="32"
+               class="avatar-img"
+               loading="lazy"
+          />
         </div>
         <span class="user-name">{props.user?.display_name}</span>
       </div>
@@ -176,14 +182,21 @@
       width: 32px;
       height: 32px;
       border-radius: var(--radius-full);
-      background: var(--accent);
-      color: white;
+      background: var(--bg-elevated);
       display: flex;
       align-items: center;
       justify-content: center;
       font-weight: 600;
       font-size: var(--text-sm);
       flex-shrink: 0;
+      overflow: hidden;
+    }
+
+    .avatar-img {
+      width: 100%;
+      height: 100%;
+      border-radius: var(--radius-full);
+      object-fit: cover;
     }
 
     .user-name {
@@ -195,6 +208,10 @@
   </style>
 
   <script>
-    export default {}
+    import { avatarFromEmail as _avatarFromEmail } from '../services/avatar.js'
+
+    export default {
+      avatarFromEmail: _avatarFromEmail,
+    }
   </script>
 </chat-sidebar>
diff --git a/client/src/components/message-bubble.riot b/client/src/components/message-bubble.riot
index 32c03e0..54bce77 100644
--- a/client/src/components/message-bubble.riot
+++ b/client/src/components/message-bubble.riot
@@ -1,6 +1,6 @@
 <message-bubble>
   <div class={'message ' + (props.message?.is_ai ? 'ai-message' : '') + (props.isOwn ? ' own-message' : '')}>
-    <div if={!props.isOwn} class="message-avatar-col">
+    <div class="message-avatar-col">
       <div class={'message-avatar ' + (props.message?.is_ai ? 'ai-avatar' : '')}>
         <svg if={props.message?.is_ai} width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
           <rect x="4" y="8" width="16" height="12" rx="2"/>
@@ -9,17 +9,21 @@
           <circle cx="9" cy="14" r="1.5" fill="currentColor"/>
           <circle cx="15" cy="14" r="1.5" fill="currentColor"/>
         </svg>
-        <template if={!props.message?.is_ai}>{props.message?.sender_name?.charAt(0).toUpperCase()}</template>
+        <img if={!props.message?.is_ai}
+             src={avatarFromHash(props.message?.avatar_hash)}
+             alt={props.message?.sender_name}
+             width="32"
+             height="32"
+             class="avatar-img"
+             loading="lazy"
+        />
       </div>
     </div>
     <div class="message-body">
-      <div if={!props.isOwn} class="message-header">
+      <div class={'message-header ' + (props.isOwn ? 'own' : '')}>
         <span class="sender-name">{props.message?.sender_name}</span>
         <span class="message-time">{formatTime(props.message?.created_at)}</span>
       </div>
-      <div if={props.isOwn} class="message-header own">
-        <span class="message-time">{formatTime(props.message?.created_at)}</span>
-      </div>
       <div if={hasToolResults()} class="tool-results-section">
         <div each={tr in getToolResults()} class="tool-result-item">
           <button class="tool-result-toggle" onclick={toggleToolResult}>
@@ -91,6 +95,14 @@
       font-weight: 600;
       font-size: var(--text-xs);
       color: var(--text-secondary);
+      overflow: hidden;
+    }
+
+    .avatar-img {
+      width: 100%;
+      height: 100%;
+      border-radius: var(--radius-full);
+      object-fit: cover;
     }
 
     .ai-avatar {
@@ -111,6 +123,7 @@
 
     .message-header.own {
       justify-content: flex-end;
+      flex-direction: row-reverse;
     }
 
     .sender-name {
@@ -308,8 +321,11 @@
 
   <script>
     import { renderMarkdown } from '../services/markdown.js'
+    import { avatarFromHash as _avatarFromHash } from '../services/avatar.js'
 
     export default {
+      avatarFromHash: _avatarFromHash,
+
       onMounted() {
         this.renderContent()
       },
diff --git a/client/src/services/avatar.js b/client/src/services/avatar.js
new file mode 100644
index 0000000..0f2821f
--- /dev/null
+++ b/client/src/services/avatar.js
@@ -0,0 +1,116 @@
+/**
+ * Gravatar avatar utilities.
+ * Uses Gravatar with "monsterid" fallback — real photos for users who have
+ * a Gravatar account, unique monster icons for everyone else.
+ */
+
+/**
+ * Get avatar URL from a pre-computed MD5 hash (used for messages).
+ * @param {string} hash - MD5 hash of the user's email (from server)
+ * @param {number} [size=64] - Pixel size
+ * @returns {string} Gravatar URL
+ */
+export function avatarFromHash(hash, size = 64) {
+  if (!hash) return `https://www.gravatar.com/avatar/?d=monsterid&s=${size}`
+  return `https://www.gravatar.com/avatar/${hash}?d=monsterid&s=${size}`
+}
+
+/**
+ * Get avatar URL from an email address (used for member list / sidebar).
+ * Computes MD5 client-side.
+ * @param {string} email - User's email
+ * @param {number} [size=64] - Pixel size
+ * @returns {string} Gravatar URL
+ */
+export function avatarFromEmail(email, size = 64) {
+  if (!email) return `https://www.gravatar.com/avatar/?d=monsterid&s=${size}`
+  const hash = md5(email.trim().toLowerCase())
+  return `https://www.gravatar.com/avatar/${hash}?d=monsterid&s=${size}`
+}
+
+// ── Compact MD5 implementation ──────────────────────────────────────────
+// Based on Joseph Myers' implementation (public domain)
+
+function md5(string) {
+  function md5cycle(x, k) {
+    let a = x[0], b = x[1], c = x[2], d = x[3]
+    a = ff(a, b, c, d, k[0], 7, -680876936);  d = ff(d, a, b, c, k[1], 12, -389564586)
+    c = ff(c, d, a, b, k[2], 17, 606105819);   b = ff(b, c, d, a, k[3], 22, -1044525330)
+    a = ff(a, b, c, d, k[4], 7, -176418897);   d = ff(d, a, b, c, k[5], 12, 1200080426)
+    c = ff(c, d, a, b, k[6], 17, -1473231341);  b = ff(b, c, d, a, k[7], 22, -45705983)
+    a = ff(a, b, c, d, k[8], 7, 1770035416);   d = ff(d, a, b, c, k[9], 12, -1958414417)
+    c = ff(c, d, a, b, k[10], 17, -42063);      b = ff(b, c, d, a, k[11], 22, -1990404162)
+    a = ff(a, b, c, d, k[12], 7, 1804603682);  d = ff(d, a, b, c, k[13], 12, -40341101)
+    c = ff(c, d, a, b, k[14], 17, -1502002290); b = ff(b, c, d, a, k[15], 22, 1236535329)
+    a = gg(a, b, c, d, k[1], 5, -165796510);   d = gg(d, a, b, c, k[6], 9, -1069501632)
+    c = gg(c, d, a, b, k[11], 14, 643717713);  b = gg(b, c, d, a, k[0], 20, -373897302)
+    a = gg(a, b, c, d, k[5], 5, -701558691);   d = gg(d, a, b, c, k[10], 9, 38016083)
+    c = gg(c, d, a, b, k[15], 14, -660478335);  b = gg(b, c, d, a, k[4], 20, -405537848)
+    a = gg(a, b, c, d, k[9], 5, 568446438);    d = gg(d, a, b, c, k[14], 9, -1019803690)
+    c = gg(c, d, a, b, k[3], 14, -187363961);  b = gg(b, c, d, a, k[8], 20, 1163531501)
+    a = gg(a, b, c, d, k[13], 5, -1444681467); d = gg(d, a, b, c, k[2], 9, -51403784)
+    c = gg(c, d, a, b, k[7], 14, 1735328473);  b = gg(b, c, d, a, k[12], 20, -1926607734)
+    a = hh(a, b, c, d, k[5], 4, -378558);      d = hh(d, a, b, c, k[8], 11, -2022574463)
+    c = hh(c, d, a, b, k[11], 16, 1839030562); b = hh(b, c, d, a, k[14], 23, -35309556)
+    a = hh(a, b, c, d, k[1], 4, -1530992060);  d = hh(d, a, b, c, k[4], 11, 1272893353)
+    c = hh(c, d, a, b, k[7], 16, -155497632);  b = hh(b, c, d, a, k[10], 23, -1094730640)
+    a = hh(a, b, c, d, k[13], 4, 681279174);   d = hh(d, a, b, c, k[0], 11, -358537222)
+    c = hh(c, d, a, b, k[3], 16, -722521979);  b = hh(b, c, d, a, k[6], 23, 76029189)
+    a = hh(a, b, c, d, k[9], 4, -640364487);   d = hh(d, a, b, c, k[12], 11, -421815835)
+    c = hh(c, d, a, b, k[15], 16, 530742520);  b = hh(b, c, d, a, k[2], 23, -995338651)
+    a = ii(a, b, c, d, k[0], 6, -198630844);   d = ii(d, a, b, c, k[7], 10, 1126891415)
+    c = ii(c, d, a, b, k[14], 15, -1416354905); b = ii(b, c, d, a, k[5], 21, -57434055)
+    a = ii(a, b, c, d, k[12], 6, 1700485571);  d = ii(d, a, b, c, k[3], 10, -1894986606)
+    c = ii(c, d, a, b, k[10], 15, -1051523);   b = ii(b, c, d, a, k[1], 21, -2054922799)
+    a = ii(a, b, c, d, k[8], 6, 1873313359);   d = ii(d, a, b, c, k[15], 10, -30611744)
+    c = ii(c, d, a, b, k[6], 15, -1560198380);  b = ii(b, c, d, a, k[13], 21, 1309151649)
+    a = ii(a, b, c, d, k[4], 6, -145523070);   d = ii(d, a, b, c, k[11], 10, -1120210379)
+    c = ii(c, d, a, b, k[2], 15, 718787259);   b = ii(b, c, d, a, k[9], 21, -343485551)
+    x[0] = add32(a, x[0]); x[1] = add32(b, x[1])
+    x[2] = add32(c, x[2]); x[3] = add32(d, x[3])
+  }
+  function cmn(q, a, b, x, s, t) {
+    a = add32(add32(a, q), add32(x, t))
+    return add32((a << s) | (a >>> (32 - s)), b)
+  }
+  function ff(a, b, c, d, x, s, t) { return cmn((b & c) | ((~b) & d), a, b, x, s, t) }
+  function gg(a, b, c, d, x, s, t) { return cmn((b & d) | (c & (~d)), a, b, x, s, t) }
+  function hh(a, b, c, d, x, s, t) { return cmn(b ^ c ^ d, a, b, x, s, t) }
+  function ii(a, b, c, d, x, s, t) { return cmn(c ^ (b | (~d)), a, b, x, s, t) }
+  function add32(a, b) { return (a + b) & 0xFFFFFFFF }
+
+  const n = string.length
+  let state = [1732584193, -271733879, -1732584194, 271733878]
+  let i
+  for (i = 64; i <= n; i += 64) {
+    md5cycle(state, md5blk(string.substring(i - 64, i)))
+  }
+  string = string.substring(i - 64)
+  const tail = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+  for (i = 0; i < string.length; i++)
+    tail[i >> 2] |= string.charCodeAt(i) << ((i % 4) << 3)
+  tail[i >> 2] |= 0x80 << ((i % 4) << 3)
+  if (i > 55) {
+    md5cycle(state, tail)
+    for (i = 0; i < 16; i++) tail[i] = 0
+  }
+  tail[14] = n * 8
+  md5cycle(state, tail)
+  return hex(state)
+
+  function md5blk(s) {
+    const md5blks = []
+    for (let i = 0; i < 64; i += 4)
+      md5blks[i >> 2] = s.charCodeAt(i) + (s.charCodeAt(i + 1) << 8) +
+        (s.charCodeAt(i + 2) << 16) + (s.charCodeAt(i + 3) << 24)
+    return md5blks
+  }
+  function hex(x) {
+    const hexChars = '0123456789abcdef'
+    let s = ''
+    for (let i = 0; i < 4; i++)
+      for (let j = 0; j < 4; j++)
+        s += hexChars[(x[i] >> (j * 8 + 4)) & 0x0F] + hexChars[(x[i] >> (j * 8)) & 0x0F]
+    return s
+  }
+}
diff --git a/server/Cargo.lock b/server/Cargo.lock
index 70bdd6b..fd276d5 100644
--- a/server/Cargo.lock
+++ b/server/Cargo.lock
@@ -480,9 +480,9 @@ dependencies = [
 
 [[package]]
 name = "deranged"
-version = "0.5.8"
+version = "0.3.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7cd812cc2bc1d69d4764bd80df88b4317eaef9e773c75226407d9bc0876b211c"
+checksum = "b42b6fa04a440b495c8b04d0e71b707c585f83cb9cb28cf8cd0d976c315e31b4"
 dependencies = [
  "powerfmt",
 ]
@@ -855,6 +855,7 @@ dependencies = [
  "dotenvy",
  "futures",
  "jsonwebtoken",
+ "md-5",
  "rand",
  "reqwest",
  "scraper",
@@ -1597,9 +1598,9 @@ dependencies = [
 
 [[package]]
 name = "num-conv"
-version = "0.2.0"
+version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf97ec579c3c42f953ef76dbf8d55ac91fb219dde70e49aa4a6b7d74e9919050"
+checksum = "51d515d32fb182ee37cda2ccdcb92950d6a3c2893aa280e540671c2cd0f3b1d9"
 
 [[package]]
 name = "num-integer"
@@ -2331,9 +2332,9 @@ checksum = "e320a6c5ad31d271ad523dcf3ad13e2767ad8b1cb8f047f75a8aeaf8da139da2"
 
 [[package]]
 name = "simple_asn1"
-version = "0.6.4"
+version = "0.6.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0d585997b0ac10be3c5ee635f1bab02d512760d14b7c468801ac8a01d9ae5f1d"
+checksum = "297f631f50729c8c99b84667867963997ec0b50f32b2a7dbcab828ef0541e8bb"
 dependencies = [
  "num-bigint",
  "num-traits",
@@ -2786,30 +2787,30 @@ dependencies = [
 
 [[package]]
 name = "time"
-version = "0.3.47"
+version = "0.3.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "743bd48c283afc0388f9b8827b976905fb217ad9e647fae3a379a9283c4def2c"
+checksum = "35e7868883861bd0e56d9ac6efcaaca0d6d5d82a2a7ec8209ff492c07cf37b21"
 dependencies = [
  "deranged",
  "itoa",
  "num-conv",
  "powerfmt",
- "serde_core",
+ "serde",
  "time-core",
  "time-macros",
 ]
 
 [[package]]
 name = "time-core"
-version = "0.1.8"
+version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7694e1cfe791f8d31026952abf09c69ca6f6fa4e1a1229e18988f06a04a12dca"
+checksum = "ef927ca75afb808a4d64dd374f00a2adf8d0fcff8e7b184af886c3c87ec4a3f3"
 
 [[package]]
 name = "time-macros"
-version = "0.2.27"
+version = "0.2.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2e70e4c5a0e0a8a4823ad65dfe1a6930e4f4d756dcd9dd7939022b5e8c501215"
+checksum = "2834e6017e3e5e4b9834939793b282bc03b37a3336245fa820e35e233e2a85de"
 dependencies = [
  "num-conv",
  "time-core",
diff --git a/server/Cargo.toml b/server/Cargo.toml
index 4f44c7f..ca0a96b 100644
--- a/server/Cargo.toml
+++ b/server/Cargo.toml
@@ -24,3 +24,4 @@ tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 rand = "0.8"
 async-trait = "0.1"
 scraper = "0.22"
+md-5 = "0.10"
diff --git a/server/src/handlers/rooms.rs b/server/src/handlers/rooms.rs
index 717d367..2a77d02 100644
--- a/server/src/handlers/rooms.rs
+++ b/server/src/handlers/rooms.rs
@@ -8,7 +8,7 @@ use uuid::Uuid;
 
 use crate::{
     middleware::auth::AuthUser,
-    models::{CreateRoomRequest, Message, MessagePayload, PaginationParams, Room, RoomResponse, UserPublic},
+    models::{CreateRoomRequest, MessagePayload, PaginationParams, Room, RoomResponse, UserPublic},
     AppState,
 };
 
@@ -177,9 +177,12 @@ pub async fn get_messages(
         return Err((StatusCode::FORBIDDEN, "Not a member of this room".into()));
     }
 
-    let messages = if let Some(before) = &params.before {
-        sqlx::query_as::<_, Message>(
-            "SELECT * FROM messages WHERE room_id = ? AND created_at < ? ORDER BY created_at DESC LIMIT ?",
+    // Query messages with user email via LEFT JOIN for Gravatar hash
+    let rows = if let Some(before) = &params.before {
+        sqlx::query_as::<_, (String, String, String, String, String, String, bool, String, Option<String>, Option<String>)>(
+            "SELECT m.id, m.room_id, m.sender_id, m.sender_name, m.content, m.mentions, m.is_ai, m.created_at, m.ai_meta, u.email \
+             FROM messages m LEFT JOIN users u ON m.sender_id = u.id \
+             WHERE m.room_id = ? AND m.created_at < ? ORDER BY m.created_at DESC LIMIT ?",
         )
         .bind(&room_id)
         .bind(before)
@@ -187,8 +190,10 @@ pub async fn get_messages(
         .fetch_all(&state.db)
         .await
     } else {
-        sqlx::query_as::<_, Message>(
-            "SELECT * FROM messages WHERE room_id = ? ORDER BY created_at DESC LIMIT ?",
+        sqlx::query_as::<_, (String, String, String, String, String, String, bool, String, Option<String>, Option<String>)>(
+            "SELECT m.id, m.room_id, m.sender_id, m.sender_name, m.content, m.mentions, m.is_ai, m.created_at, m.ai_meta, u.email \
+             FROM messages m LEFT JOIN users u ON m.sender_id = u.id \
+             WHERE m.room_id = ? ORDER BY m.created_at DESC LIMIT ?",
         )
         .bind(&room_id)
         .bind(params.limit)
@@ -197,23 +202,27 @@ pub async fn get_messages(
     }
     .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
 
-    let payloads: Vec<MessagePayload> = messages
+    let payloads: Vec<MessagePayload> = rows
         .into_iter()
         .rev()
-        .map(|m| {
-            let ai_meta = m.ai_meta
+        .map(|(id, room_id, sender_id, sender_name, content, mentions, is_ai, created_at, ai_meta_str, email)| {
+            let ai_meta = ai_meta_str
                 .as_deref()
                 .and_then(|s| serde_json::from_str::<crate::models::AiMeta>(s).ok());
+            let avatar_hash = email
+                .map(|e| crate::models::gravatar_hash(&e))
+                .unwrap_or_default();
             MessagePayload {
-                id: m.id,
-                room_id: m.room_id,
-                sender_id: m.sender_id,
-                sender_name: m.sender_name,
-                content: m.content,
-                mentions: serde_json::from_str(&m.mentions).unwrap_or_default(),
-                is_ai: m.is_ai,
-                created_at: m.created_at,
+                id,
+                room_id,
+                sender_id,
+                sender_name,
+                content,
+                mentions: serde_json::from_str(&mentions).unwrap_or_default(),
+                is_ai,
+                created_at,
                 ai_meta,
+                avatar_hash,
             }
         })
         .collect();
diff --git a/server/src/handlers/ws.rs b/server/src/handlers/ws.rs
index 8d4e705..151aaed 100644
--- a/server/src/handlers/ws.rs
+++ b/server/src/handlers/ws.rs
@@ -37,10 +37,10 @@ pub async fn ws_handler(
         }
     };
 
-    ws.on_upgrade(move |socket| handle_socket(socket, state, claims.sub, claims.display_name))
+    ws.on_upgrade(move |socket| handle_socket(socket, state, claims.sub, claims.display_name, claims.email))
 }
 
-async fn handle_socket(socket: WebSocket, state: Arc<AppState>, user_id: String, display_name: String) {
+async fn handle_socket(socket: WebSocket, state: Arc<AppState>, user_id: String, display_name: String, email: String) {
     let (mut ws_tx, mut ws_rx) = socket.split();
     let mut broadcast_rx = state.tx.subscribe();
 
@@ -78,6 +78,7 @@ async fn handle_socket(socket: WebSocket, state: Arc<AppState>, user_id: String,
     let state_clone = state.clone();
     let user_id_clone = user_id.clone();
     let display_name_clone = display_name.clone();
+    let email_clone = email.clone();
     let rooms_clone2 = subscribed_rooms.clone();
 
     // Task: receive messages from client
@@ -127,6 +128,7 @@ async fn handle_socket(socket: WebSocket, state: Arc<AppState>, user_id: String,
                         &state_clone,
                         &user_id_clone,
                         &display_name_clone,
+                        &email_clone,
                         &room_id,
                         &content,
                         &mentions,
@@ -150,6 +152,7 @@ async fn handle_send_message(
     state: &Arc<AppState>,
     user_id: &str,
     display_name: &str,
+    email: &str,
     room_id: &str,
     content: &str,
     mentions: &[String],
@@ -183,6 +186,8 @@ async fn handle_send_message(
         is_ai: false,
         created_at: now,
         ai_meta: None,
+        avatar_hash: crate::models::gravatar_hash(email),
+
     };
 
     let _ = state.tx.send(BroadcastEvent {
@@ -408,6 +413,7 @@ async fn handle_send_message(
         is_ai: true,
         created_at: ai_now,
         ai_meta,
+        avatar_hash: String::new(),
     };
 
     let _ = state.tx.send(BroadcastEvent {
diff --git a/server/src/models/mod.rs b/server/src/models/mod.rs
index 6a2c2fa..0dfb230 100644
--- a/server/src/models/mod.rs
+++ b/server/src/models/mod.rs
@@ -205,6 +205,16 @@ pub struct MessagePayload {
     pub created_at: String,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub ai_meta: Option<AiMeta>,
+    #[serde(default)]
+    pub avatar_hash: String,
+}
+
+/// Compute Gravatar-compatible MD5 hash from an email address.
+pub fn gravatar_hash(email: &str) -> String {
+    use md5::{Md5, Digest};
+    let normalized = email.trim().to_lowercase();
+    let result = Md5::digest(normalized.as_bytes());
+    format!("{:x}", result)
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]